In recent years, as an electronic device as typified by a personal computer has been improved in performance, a calorific value of a CPU (heat-generating element) installed therein has been increased in amount. Moreover, hybrid vehicles, electric vehicles, and high-speed railroad vehicles employ a power semiconductor with a large calorific value for a switching operation of a motor. To stably operate an electronic device with a large calorific value, a cooling device with a high reliability has been required.
In a conventional art, a heat sink of an air cooling fan system has been used to cool heat-generating elements, but problems such as noises caused by the fan and cooling limits by the air cooling system have gain prominent attention. Thus, a water-cooled plate of a water cooling system (liquid-cooled jacket) has gathered attention as a next-generation cooling system.
For example, Patent Literature 1 discloses a liquid-cooled jacket adapted to cool heat-generating elements. FIG. 50 is a cross-sectional view showing a conventional liquid-cooled jacket. As shown in FIG. 50, the conventional liquid-cooled jacket 300 is composed of a jacket body 310, and a sealing body 320 that covers recesses of the jacket body 310. The jacket body 310 has grooves 311 formed therein. The sealing body 320 is composed of a substrate 321, and a plurality of fins 322 formed perpendicularly to the substrate 321.
The jacket body 310 and the sealing body 320 are joined together by frictional stirring. A heat-generating element H has a flange H1 which is fixed to the grooves 311 with screws (fitting members) M.